Geology Reference
In-Depth Information
pearedsomethinglikethemodernredplanetMars,butwithblueoceansandswirlingwhite
clouds that provided dramatically colorful contrasts.
Rust was only the most obvious of many profound mineralogical changes. Our recent
chemical modeling suggests that the Great Oxidation Event paved the way for as many as
threethousandminerals,allofthemspeciespreviouslyunknowninourSolarSystem.Hun-
dreds of new chemical compounds of uranium, nickel, copper, manganese, and mercury
arose only after life learned its oxygen-producing trick. Many of the most beautiful crystal
specimens in museums—blue-green copper minerals, purple cobalt species, yellow-orange
uranium ores, and others—speak powerfully of a vibrant living world. These newly min-
ted minerals are unlikely to form in an anoxic environment, so life appears to be respons-
ible, directly or indirectly, for most of Earth's forty-five hundred known mineral species.
Remarkably, some of these new minerals provided evolving life with new environmental
niches and new sources of chemical energy, so life has continuously coevolved with the
rocks and minerals.
Oxygen, a magically transformative element, plays the starring role in this drawn-out
history. Hungry for electrons, oxygen atoms react vigorously with all manner of minerals,
thus weathering away rocks and forming nutrient-rich soils in the process. When concen-
trations of atmospheric oxygen first rose to significant levels more than two billion years
ago, all photosynthetic life-forms lived in the oceans. The lands were absolutely barren of
life. But oxygen paved the way for life's eventual expansion across the globe.
Today we experience oxygen in the most intimate exchange. With every breath we take,
a tiny portion of the air becomes a part of us, even as a tiny part of us becomes the air. As
dayspass,ourbodiesmeltawayandformagaininmoment-by-moment chemical reactions
with oxygen. Our tissues are replaced over and over again throughout our lives, Earth's
finite store of atoms recycling among air, sea, land, and all its living forms. Most of the
atoms that formed your infant body at birth are now dispersed, as your present atoms will
be again, if you have the good fortune to live a few more years on this oxygen-rich planet-
ary home.
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